protected function prepareRequestHeaders(RequestInterface $request)
{
// @see http://en.wikipedia.org/wiki/User_agent
$request->setHeader('User-Agent', sprintf('%s/%s (PHP %s)', self::NAME, self::VERSION, phpversion()));
$request->setHeader('X-BitPay-Plugin-Info', sprintf('%s/%s', self::NAME, self::VERSION));
$request->setHeader('Content-Type', 'application/json');
$request->setHeader('X-Accept-Version', '2.0.0');
}